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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        /*
        
            A : var this = 10; //this关键字

            B : var For = 10; //对的

            C : var _num = 10; //对的

            D : var 变量  = 10; //对的

            E : var $total = 10;//对的

            F : var 9all = 10; //开头是数字，所以错了

            G: var background-color = 'red'; // 不能出现-
        */

        // var _this = 10;

        // var For = 10;
    
        // var _num = 10;

        // var 变量 = 10;

        // var $total = 10;

        // var _9all = 10;

        // var backgroundColor = 'red';







        var v1, v2, v3 = 'hello',
            v4 = 42,
            v5;

        console.log(v1);
        console.log(v2);
        console.log(v3);
        console.log(v4);
        console.log(v5);


    </script>
</body>
</html>